Low-volume goat milk transmission of classical scrapie to lambs and goat kids

Abstract

The risk of classical scrapie transmission in small ruminants is highest during the neonatal period with the placenta recognized as a significant source of infection. Milk has also been identified as a source of scrapie with sheep-to-sheep transmission occurring after neonatal consumption of as little as 1–2 liters of milk; concurrent mastitis due to small ruminant lentivirus (SRLV) infection may be associated with increased scrapie transmission via milk in sheep. In contrast, goat-to-sheep transmission has been documented only after prolonged consumption of >30 liters of milk. The goal of the current study was to assess transmission of scrapie to goat kids and lambs following low volume, short duration consumption of milk from infected goats. Milk from two does (female goats) with pre-clinical scrapie was fed to four goat kids (≤4.5 L each) and four lambs (~3.7 L each) beginning ~24 hours after birth. Scrapie transmission was detected in three sheep as early as 18 months post inoculation; transmission was also detected in two goats but not until postmortem analyses at 33 months post inoculation. Each milk donor goat also had naturally-acquired infection with SRLV. Different degrees of lymphohistiocytic inflammation and PrPSc accumulation were observed in mammary gland tissues of the donors, which appeared to associate with transmission of scrapie via milk. Thus, similar to the risks of milk transmission of scrapie from sheep, even limited exposure to milk from goats can pose significant risk for scrapie transmission to both goat kids and lambs.

Evaluation of Antemortem Diagnostic Techniques in Goats Naturally Infected With Scrapie

“…Sheep and goats are typically thought to be infected with scrapie as lambs or kids via contact with the placenta or placental fluids. However, evidence suggests that both sheep and goats can be infected from ingestion of prions shed in bodily fluids [e.g., milk (1)(2)(3)(4)(5)(6), saliva (7), and feces (8)] and contaminated environments (9,10), such as pastures. Animals that may be shedding the scrapie agent and are asymptomatic are rarely identified until the onset of clinical signs, substantially increasing risk of transmission.…”

Classical and Atypical Scrapie in Sheep and Goats. Review on the Etiology, Genetic Factors, Pathogenesis, Diagnosis, and Control Measures of Both Diseases

“…Studies estimated that the main sources of environmental contamination in classical scrapie disease are placentas [ 94 , 95 , 96 ], feces [ 97 ], and carcasses of infected animals [ 98 ]. Research demonstrated that the prion protein is also eliminated through excretions (feces and urine) or secretions (milk and saliva) [ 66 , 97 , 99 , 100 , 101 , 102 , 103 , 104 ] and semen [ 105 ].…”

“…The presence of PrP Sc in the mammary glands of co-infected scrapie animals with maedi-visna [ 181 ] suggested that milk could serve as a potential transmission vehicle of scrapie. In addition, the presence of PrP Sc in the distal ileum and rectal mucosa from lambs with susceptible genotypes fed with milk from scrapie-affected females demonstrated the transmission of the disease through this route [ 66 , 99 , 100 ].…”

Scientific report on the analysis of the 2‐year compulsory intensified monitoring of atypical scrapie

“…CS transmits horizontally, under field conditions, due to the ingestion of PrP Sc either directly from secreta/excreta from infected animals, most notably the presence of PrP Sc in the placenta of infected sheep and goats (Tuo et al., 2002 ; Schneider et al., 2015 ), via milk (Konold et al., 2008 , 2013; Madsen‐Bouterse et al., 2018 ), or via environmental contamination with such infected materials (Touzeau et al., 2006 ; Dexter et al., 2009 ; Konold et al., 2015 ).…”